Various techniques have been proposed and put into practical use for the purpose of observation and detection of lesional states of biological tissues. In particular, endoscope which is inserted into internal hollow organs, captures images of biological tissues and transmits the acquired images has widely been disseminated. The techniques having been proposed are directed not only to image diagnosis merely based on visible light, but also to techniques with wise use of ultrasonic wave, florescence or spectral light. In particular, the method making use of fluorescence takes an advantage of capability of real-time diagnosis.
In the fluorescence-assisted diagnosis, an excitation light is illuminated on a site of measurement so as to induce therefrom emission of fluorescence, and wavelength and intensity of the emitted fluorescence are analyzed. Probe has been developed for the convenience of such diagnosis, and has been used for diagnosing lesional states of biological tissues and status of disease of cancer and so forth (types of disease, range of invasion, etc.).
This sort of probe incorporates an illuminating optical fiber, a receiving optical fiber and a lens. Excitation light output from the end of the illuminating optical fiber is cast onto a site to be measured of a biological tissue, and the fluorescence emitted from the site to be measured of the biological tissue is cast through the lens onto to the end of the receiving optical fiber.
Patent Document 1 discloses a technique of immobilizing two optical fibers to a ferrule, but with no disclosure on immobilization of the lens.
Patent Document 2 discloses a technique of disposing a coupling lens ahead of the end faces of two optical fibers, with one optical fiber aligned with the axis of a ferrule, the other optical fiber decentered from the axis of the ferrule, the end faces of these two optical fibers and the ferrule are aligned, and these end faces are inclined with respect to the optical axis of the optical fiber.
Patent Document 3 discloses a technique of disposing a plurality of lenses between one multi-mode optical fiber and an LED, so as to condense light emitted from the LED through the plurality of lenses onto the end of the multi-mode optical fiber.